Mhm, I haven't seen many other games out right now that do weather, or if they do, it's not that fleshed out.
For weather/wetness having gameplay effects in the future, I was thinking maybe heavy fog could help obscure the player. I'm not really sure what I could do with the player being wet, but I am open to suggestions.
Maybe focus on what the weather will do to npcs instead? For instance, rain makes some npcs run to get out of the rain or cover their heads, reducing their vision? Maybe more npcs in areas of the map where they're sheltered from the rain and less npc in unsheltered areas? Npcs grouping up and "waiting out" the rain
If snow is an idea, maybe add hidden moving spots around the map where there's a small chance of slipping and falling (you can't cover yourself until you've stood back up)